Applications of fluorescent sensor based on 1H-pyrazolo[3,4-b]quinoline in analytical chemistry

Fluorescent Sensor Based on 1H-Pyrazolo[3,4-b]quinoline Derivative for Detecting Zn2+ Cations

The photophysical and sensory properties of the donor-acceptor pyrazoloquinoline derivative (PQPc) were investigated using absorption, steady-state, and time-resolved fluorescence measurements. The compound synthesized from commercial, readily available substrates exhibited absorptions in the UV-Vis range, with a maximum of the longwave band around 390 nm. The maximum fluorescence was around 460-480 nm, depending on the solvent. The quantum yield was between 12.87% (for n-hexane) and 0.75% (for acetonitrile) and decreased with increasing solvent polarity. The PET mechanism was implicated as the cause of fluorescence quenching. Divalent ions such as Zn2+, Pb2+, Cd2+, Ca2+, Mg2+, Co2+, Ni2+, and Cu2+ were introduced to study the fluorescent response of PQPc. A 13-times increase in fluorescence quantum yield was observed after the addition of Zn2+ ions. Detailed research was carried out for the PQPc-Zn2+ system in order to check the possibility of analytical applications of PQPc as a fluorescent sensor. A detection limit of Zn2+ was set at the value level 1.93 × 10-7 M. PQPc-Zn2+ complexes had a stoichiometry of 1:1 with a binding constant of 859 M-1. Biological studies showed that the sensor was localized in cells near the membrane and cytoplasm and may be used to detect zinc ions in eukaryotic cells.

1H-Pyrazolo[3,4-b]quinolines: Synthesis and Properties over 100 Years of Research

This paper summarises a little over 100 years of research on the synthesis and the photophysical and biological properties of 1H-pyrazolo[3,4-b]quinolines that was published in the years 1911–2021. The main methods of synthesis are described, which include Friedländer condensation, synthesis from anthranilic acid derivatives, multicomponent synthesis and others. The use of this class of compounds as potential fluorescent sensors and biologically active compounds is shown. This review intends to summarize the abovementioned aspects of 1H-pyrazolo[3,4-b]quinoline chemistry. Some of the results that are presented in this publication come from the laboratories of the authors of this review.

A novel fluorescent probe with a pyrazolo[4,3-c]quinoline core selectively recognizes c-MYC promoter G-quadruplexes

An aptamer combined with a c-MYC-selective fluorophore could work as the fluorescent core of nucleic acid mimics of fluorescent proteins to locate and image functional biomolecules in cells.

Pyrazoline-based colorimetric and fluorescent probe for detection of sulphite

This work reports a novel Michael addition based sensor for fluorescence detection of sulphite in river water samples.

Stationary and time-resolved spectra analysis of pyrazoloquinoline derivatives with pyridyl moiety

Two derivatives of pyrazoloquinoline with pyridyl moiety: 6-N,N-dimethyl-3-phenyl-1-(2-pyridyl)-1H-pyrazolo[3,4-b]quinoline (DMA-1PPhPQ) and 6-N,N-dimethyl-1,3-(di-2-pyridyl)-1H-pyrazolo[3,4-b]quinoline (DMA-1,3PPQ) were synthesized with commercial substrates. The theoretical characterization of both compounds was done. Geometry optimizations give not flat structure with the first absorption band at the wavelength about 390nm for both compounds. Several electro-optical parameters were also calculated. The optical properties of DMA-1PPHPQ and DMA-1,3PPQ were investigated by ultraviolet-visible spectroscopy and stationary as well as time-resolved fluorescence. The fluorescence maximum and fluorescence quantum yield are strongly dependent on solvent polarity function. Results indicate CT fluorescence for both compounds. Because of high emission the investigated pyrazoloquinoline derivatives can be potential candidates for fabrications of electroluminescent devices.